The proposed work is directed toward identification and quantitation of binding proteins in the lung. Cell fragments with high affinity for serotonin have been identified in the 30,000 x g pellet of pig lung homogenate. This fraction is rich in converting enzyme activity, a marker for the endothelial cell surface. Attempts will be made to characterize this binding site further and establish that it represents a protein in the endothelial cell membranes. A protein with high affinity for palmitic acid has been identified in the 106,000 x g supernatant of rat and rabbit lung homogenate. Studies will be carried out to establish the molecular weight of this protein and cross reactivity with other ligands. The protein will be purified for preparation of antibodies to establish its location in intact lung cells. BIBLIOGRAPHIC REFERENCES: Hays, R.M., Levine, S.D., Myers, J.D., Heinemann, H.O., Kaplan, M.A., Franki, N. and Berliner, H. Urea transport in the dogfish kidney. J. Exp. Zool. 199: 309-316, 1977. Wagner, M.E. and Heinemann, H.O. The effect of potassium on utilization of (1-14C) palmitic acid in renal cortex of the rat. Am. J. Physiol. 1: F254-F259, 1977.